19 Gene Structure, prokaryotic vs. eukaryotic

Question 1

The eukaryotic nucleus is analogous to the prokaryotic ____

Answer 1

nucleoid

Question 2

What is the size difference between eukaryotic and prokaryotic genomes due to?

Answer 2

• The presence of more genes in eukaryotic genomes (in general)
• Differences in gene and genome structure

Question 3

Prokaryotic genes are often arranged in ___

Answer 3

operons

Question 4

What is an operon?

Answer 4

A group of gene expressed in conjunction with one another. Often encoding proteins involved in the same biochemical process or pathway (eg. Lac operon).

Prokaryotic method of gene arrangement

Question 5

What are mRNA that can contain information for more than one protein called?

Answer 5

Polycistronic mRNAs

Question 6

True or false? mRNA is co-linear with the DNA of an organism? (eg. there are no intervening sequences such as introns)

Answer 6

True

Question 7

What level does prokaryotic regulation of gene expression occur? What mediates this?

Answer 7

The level of transcription initiation and control. Mediated by the binding of trans-acting factors at cis-acting sites

Question 8

True or false? Prokaryotic mRNA does not undergo post-transcriptional modification

Answer 8

True, prokaryotic mRNA does not undergo post transcriptional modification

Question 9

Transcription and translation are _____ in prokaryotes

Answer 9

coupled

Occur simultaneously

Question 10

What are the steps that take template DNA to mature mRNA in eukaryotes?

Answer 10

• Transcription of DNA by RNA polymerase
• 5’ capping
• Intron splicing, 3’ cleavage and 3’ polyadenylation of primary mRNA transcript

Question 11

What eukarotic post-transcriptional modification to mRNA positions the mRNA on the ribosome?

Answer 11

7-methylguanosine cap to the 5’ end of the transcript

Question 12

What adds the 3’ poly(A) tail to eukaryotic mRNA?

Answer 12

poly (A) polymerase

Question 13

Where are regulatory elements positioned relative to genes? (eg. upstream or downstream)

Answer 13

Upstream and downstream

Question 14

Where is regulation of gene expression in eukaryotes? Are factors trans or cis acting? Sites?

Answer 14

• Level of transcription initiation and control
• Trans acting factors
• Cis acting sites

Question 15

Where do posttranscriptional modification of eukaryotic mRNA take place?

Answer 15

The nucleus

Question 16

How can splicing modify genes?

Answer 16

Genes in different tissues can splice differently in a phenomenon called alternative splicing

Question 17

In prokaryotes, what processing happens to rRNA?

Answer 17

• Methylation and pseudouridine conversion
• Cleavage (formation of intermediates = subunits)
• Nucleases digest intermediates to produce mature rRNAs and tRNA from pre-rRNA transcript

Question 18

How many base pairs are there in the human genome?

Answer 18

About 3200 mega base pairs (Mgp)

Question 19

What percent of human genome is repeated sequences?

Answer 19

50%